This invention relates to a process for preparing electrically conductive shaped articles such as films or fibrous material from a polybenzimidazole, and to the conductive shaped articles produced thereby. The invention further relates to an electrically conductive composite comprising electrically conductive polybenzimidazole fibrous material and to a process for preparing such material. The invention is useful for EMI shielding and static dissipation, in forming electrically conductive resins and paints, and as a membrane in certain gas or liquid separations.
It is known in the art to plate copper metal onto various polymeric substrates. For example, Davis U.S. Pat. No. 4,143,186 discloses a process for electroless plating of copper on substrates such as polyimides and polyparabanic acids (polyimidazoletriones) comprising deposition of copper in an acidic bath containing a divalent copper salt such as copper sulfate and a reducing agent such as dimethyl amine borane, wherein the copper salts may be present in a concentration of between 0.05 and 0.15M.
Further, McCormack et al U.S. Pat. No. 4,301,196 discloses a process for electroless plating of copper by employing a bath comprising copper ions, a reducing agent, a pH adjustor, and a depolarizing agent. The depolarizing agent can be 1,3-imidazole, benzimidazole, and the like (Column 4, lines 24-45). The process may be employed to electrolessly deposit copper on paper, glass, or synthetic resins and plastics including nylons, acrylic, Mylar.RTM. polyester film, and epoxies (Column 7, lines 31-136). See also, U.S. Pat. Nos. 3,736,170; 3,993,801; 4,199,623; 4,209,331; and 4,261,800, which disclose various processes for electroless deposition of copper onto polymeric substrates.
U.S. Pat. No. 4,374,893 discloses the preparation of textiles based upon synthetic polymers such as polyesters and polyamides, having a surface coating of at least 3 percent copper sulfide, the composition of which is such that the atomic ratio Cu/S is between 1.5 and 2, preferably more than 1.7. The copper sulfide is formed by a process comprising treatment with hydrogen sulfide, followed by contact with at least one reducing agent and copper cations provided by a copper salt.
It is also known to form metal salt complexes of alkylbenzimidazole polymers wherein such salts may be prepared by mixing dimethylsulfoxide solutions of an inorganic metal salt and subsequently stripping off the DMSO solvent such that metal is complexed within the benzimidazole rings. Suitable metal cations include Cu(II), Zn(II), and Cd(II). The electrical resistivity of the resultant salt may be increased by a factor of twenty or more relative to the neutral polymer. [Aharoni et al, "Electrical Resistivities and ESCA Studies on Neutral Poly(alkylbenzimidazole), Their Salts and Complexes," Journal of Applied Polymer Science, Volume 23, 2363-2660 (1979)].
It is therefore an object of the present invention to provide a process for preparing an improved highly electrically conductive shaped article such as a film or fibrous material.
It is a still further object of the present invention to provide a process for preparing a improved electrically conductive shaped article which is flexible and ductile.
It is a further object of the present invention to provide an improved electrically conductive shaped article having high levels of covellite copper sulfide in association therewith, wherein the copper sulfide is substantially entirely in the form of covellite copper sulfide.
It is a still further object of the invention to provide a process for preparing a composite article which incorporates an improved electrically conductive fibrous material which is heat stable and which may be processed in a molten resinous matrix without destruction of the fibrous material.
It is a still further object of the invention to provide an electrically conductive monolithic composite incorporating an improved electrically conductive fibrous material.
It is a still further object of the invention to provide an electrically conductive polymer composition incorporating an improved electrically conductive fibrous material.
It is a still further object of the invention to produce conductive shaped articles which are suitable for use in EMI shielding applications and other applications where electrically conductive media are desired.
It is a still further object of the invention to produce a conductive film which is suitable for use in gas or liquid separators.
It is another object of the invention to produce patterned conductor film or sheet material for use as heating elements or in electronic circuitry such as printed circuit boards.
These and other objects, as well as the scope, nature, and utilization of the claimed invention will be apparent to those skilled in the art by the following detailed description and appended claims.